High Lockout
Fault 33 / 22 on Worcester Bosch Greenstar CDi Compact

Your boiler's computer is confused because it thinks internal temperature sensors are plugged into the wrong place, preventing the unit from operating safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Temperature sensors incorrectly connected: A temperature sensor is connected to the IUM.

What causes this fault?

This fault occurs when the boiler's control board detects that the internal temperature sensors are plugged into the wrong terminals or have been cross-wired. It is almost always caused by a component failure within the internal computer module or a wiring harness that has worked loose or degraded over time.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

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